One of the central issues in neurobiology revolves around the importance of trophic molecules in the survival and differentiation of developing, injured and aged dopamine neurons. Moreover, the absence or loss of growth factors has been implicated as a possible cause for a) the degeneration of neurons that occurs in a number of neurodegenerative diseases like Parkinson's and b) the failure of implanted brain cells to survive in transplant therapy. The research proposed in this application is intended to examine the role of growth substances (EGF, aFGF, bFGF, TGFbeta, CNTF, LIF, IL1, NGF, IGF, GM1) in regulating the survival and biochemical differentiation of dopamine neurons during development, after damage, and following transplantation. The primary model to be used in these studies is one which we have only recently developed wherein populations of nearly pure dopamine neurons are isolated for study. This is accomplished by flow cytometry of neurons previously labeled with retrogradely transported fluorescent dyes (diI). Until now, dopamine neurons have comprised only a small (<1%) fraction of midbrain neurons used in these studies. With this new found ability to isolate nearly purified (>90%) dopamine neurons, we are now In an Ideal position to examine the relative contributions made directly by dopamine neurons or Indirectly by other cell types and/or their molecular products (ie. trophic factors). These cellular/molecular relationships in the dopamine system will be studied as they relate to l) normal development; 2) abnormal development in the Weaver mutant mouse; recovery after damage and 4) transplantation into the lesioned brain. We will use a multidisciplinary approach to evaluate dopamine function in vivo and in vitro, including anatomical (immunocytochemistry, in situ hybridization, receptor autoradiography), biochemical (radioenzymatic assay, HPLC-EC, receptor binding assays, uptake assays) and molecular (Northern analysis, in situ hybridization) and behavioral (motor) methods of analysis. The long range goal of this work is to elucidate the cellular and molecular processes regulating the survival and differentiation in the developing and injured dopamine system. These studies will hopefully lay the foundation for the development of therapeutic treatments for the compromised dopamine system found in Parkinson's and Alzheimer's disease and other disorders of the aging brain.